An organic light-emitting device (OLED), which is a new lighting and display technology, has unique advantages and has been widely adopted. It is a current research subject to improve the performance of the OLED. A packaging process has an important influence on a service life of the OLED, wherein the stability of dripping of a packaging adhesive largely affects the result of the packaging process.
As shown in FIG. 1, a conventional adhesive feeding device includes a storage tank 3 for storing a liquid adhesive, an adhesive dripping unit 1 for dripping the adhesive, and a control unit (e.g., an electromagnet 2) for controlling the adhesive dripping unit 1. The storage tank 3 is connected to the adhesive dripping unit 1 through a transfer tube 4, and the liquid adhesive is transferred from the storage tank 3 to the adhesive dripping unit 1 by introducing N2 (nitrogen gas) into the storage tank 3.
The adhesive dripping unit 1 includes a container 12 for accommodating the liquid adhesive, the container 12 having an opening 13 at one end and a nozzle 11 at the other end, and a connector 14 firmly connected to the opening 13 of the container 12.
The adhesive dripping unit 1 further includes a firing pin 15 provided inside the container 12. The firing pin 15 moves up and down under control of a magnetic field generated from the electromagnet 2, so as to extrude a predetermined amount of the liquid adhesive from the nozzle 11, thereby controlling the dripping of the liquid adhesive.
The electromagnet 2 includes a core 21 and a spiral wire 22 wound around the core 21. As shown in FIG. 1, the electromagnet 2 is located above the adhesive dripping unit 1, and the up-and-down reciprocal movement of the firing pin 15 is controlled by changing a direction of an electric current passing through the spiral wire 22. For example, the electric current passing through the spiral wire 22 may be a square wave current. Further, a speed of the movement of the firing pin 15 may be changed by changing the magnitude of the electric current passing through the spiral wire 22, thereby controlling a speed of the dripping of the liquid adhesive.
During an adhesive dripping process in which an adhesive dripping method is performed by using the conventional adhesive feeding device, a large amount of heat may be generated due to impingement by the firing pin 15, and thus physicochemical parameters such as viscosity and density of the liquid adhesive are degraded, causing a deviation of dripping control to occur. Further, wear of the firing pin 15 and the nozzle 11 is likely to occur, which will increase the maintenance cost.
Moreover, the liquid adhesive in the storage tank 3 is transferred from the storage tank 3 to the container 12 by being applied with pressure using N2. In this case, the instability of the pressure of N2 and the deformation or leakage of the storage tank 3 will cause the transfer of the liquid adhesive to fluctuate and be difficult to control.